Rainfall sensor based on friction nanometer generator

Abstract

The invention provides a rainfall sensor based on a friction nanometer generator (TENG), and aims to solve the problems that an existing TENG rainfall sensor is low in accuracy and poor in stability, and energy supply is limited when the existing TENG rainfall sensor serves as an energy harvester. The sensor is composed of a rainfall intensity sensing unit, a rainfall sensing unit and a protective cylinder. In the rainfall intensity sensing unit, the positive correlation between the rainfall intensity and the TENG electric signal frequency is established by adopting the cooperative work of a sensing rough measurement part and a sensing accurate measurement part, so that the high-precision real-time measurement of the rainfall intensity is realized. The rainfall is converted into periodic water flow through a siphon emptying event of the siphon cup, and a relationship is further established between the periodic water flow and the TENG electric signal frequency of the rainfall sensing unit, so that stable and reliable measurement of the rainfall is realized. The design of the sensor effectively overcomes the problem that a traditional rain gauge is sensitive to humidity, and ensures the accuracy and stability of measurement. Meanwhile, the rainfall sensing unit can convert the outlet flow of the siphon cup into TENG voltage, the efficiency of converting rainwater energy into electric energy is improved, the device can serve as a stable energy harvester, and power support is provided for other low-power-consumption sensors in a wireless sensing network. In conclusion, the rainfall sensor has the remarkable advantages of humidity interference resistance, high energy conversion efficiency and self-driving function, and a practical and reliable solution is provided for wireless sensing detection of rainfall information.

Description

Technical Field

[0001] The present invention relates to the technical field of rainfall sensors, and particularly to a rainfall sensor based on a triboelectric nanogenerator. Background Art

[0002] The acquisition and utilization of rainfall information are of extremely important significance in the fields of agricultural production, water resource management, weather forecasting, meteorological monitoring, and natural disaster prevention. Accurate rainfall information data can not only guide agricultural managers to reasonably arrange irrigation and fertilization to increase crop yields, but also provide a scientific basis for the effective management of water resources. Moreover, it can also help government meteorological departments and security departments to timely issue weather forecasts and early warning information, thereby reducing the impact of natural disasters on human production and life. A rain gauge is a sensor that can obtain rainfall information and can be used as a node in a wireless sensor network for intelligent agricultural monitoring. According to its different working principles, existing rain gauges can be mainly divided into various types such as mechanical, electrical, and optical. The siphon rain gauge is a typical representative of the mechanical rain gauge type and can accurately measure rainfall, rainfall intensity, and the start and end times of precipitation based on the siphon principle. Since the siphon rain gauge can directly detect the weight or volume of rainwater without physical quantity conversion, it has extremely high measurement accuracy from the perspective of the measurement principle and has thus been widely used in the hydrological and meteorological fields. In addition, its remarkable advantages also include strong compatibility with precipitation patterns (hail, snow, rainfall, etc.), simple structure, low cost, and convenient construction. Especially, since there are no mechanical moving parts in the siphon tube, the working stability, durability, and service life of the device are greatly enhanced, making it particularly suitable for long-term deployment in a wireless sensor network for rainfall information.

[0003] However, traditional rain gauges usually rely on battery power to function, which gives rise to problems such as battery replacement, maintenance, and pollution, severely restricting their further development and application in rainfall information wireless sensor networks. To solve the above problems, the use of new self-driven sensing technology to achieve the sensing and detection of rainfall information has attracted extensive interest and attention from scholars. Among the rainfall sensors proposed in recent years, the triboelectric nanogenerator (TENG), as a new type of self-driven sensing technology, has demonstrated its great advantages and potential in rainfall information measurement. Traditional TENG-based rainfall sensors work through the contact mode at the liquid-solid interface. Utilizing the triboelectrification and electrostatic induction principles between raindrops and friction materials, they can convert the mechanical energy and charge energy of rainwater into electrical energy, and by establishing a positive correlation between the TENG voltage signal and rainfall intensity, the detection of rainfall information is achieved. Although traditional TENG rainfall sensors can detect rainfall amount, rainfall intensity, and the start and end times of rainfall, showing good application prospects, two key problems need to be solved at present: First, the traditional TENG rainfall sensing principle relies on voltage amplitude detection, and the voltage amplitude is extremely susceptible to environmental factors such as humidity changes. Especially in the high-humidity environment during rainfall, this high sensitivity to humidity will greatly cause measurement errors, resulting in low accuracy and precision of measurement results and poor stability; Second, traditional TENG rainfall sensors can also be used as energy harvesters to convert raindrop energy into electrical energy. However, due to the characteristics of raindrop energy being random, discrete, low energy density, and limited terminal velocity, the energy conversion efficiency of the device for rainwater energy utilization is low, and the power supply for other sensors in the rainfall information wireless sensor network is limited. Therefore, in response to the above problems, there is an urgent need to develop new self-driven rainfall sensors to overcome the limitations of existing technologies to achieve more stable and reliable rainfall information acquisition and rainwater energy utilization. Summary of the Invention

[0004] The technical objective to be achieved by the present invention is to solve the problems of low accuracy, poor stability, and limited energy supply as an energy harvester in existing TENG rainfall sensors, and to propose a rainfall sensor based on a triboelectric nanogenerator. The device is mechanically designed with two sensing units for rainfall intensity and rainfall amount. In the rainfall intensity sensing unit, through the coordinated cooperation of the sensing rough measurement component and the sensing precise measurement component, a positive correlation between the rainfall sensing intensity and the TENG electrical signal frequency in this unit can be established, realizing real-time measurement of a large range and high precision of rainfall intensity; the siphon cup in this unit can convert the event of emptying the rainfall in the environment through siphon into periodic outlet water flow into the rainfall amount sensing unit, thereby establishing a positive correlation between the outlet flow rate and the TENG electrical signal frequency in the rainfall amount sensing unit. Therefore, the TENG electrical signal frequency can be used to characterize the rainfall amount in the environment, and at the same time, stable and reliable real-time measurement of the rainfall amount can be achieved because environmental factors such as humidity do not affect the frequency. In addition, the rainfall amount sensing unit can convert the outlet flow rate of the siphon cup structure into a voltage signal of the TENG, and finally, it can realize the conversion of random, discrete, and low-level rainwater energy into regular, ordered, and high-level electrical energy.

[0005] The technical patent provided by the present invention is as follows: A rainfall sensor based on a triboelectric nanogenerator, mainly composed of a rainfall intensity sensing unit, a rainfall amount sensing unit, and a protective cylinder.

[0006] The rainfall intensity sensing unit consists of a rough sensing component, a precise sensing component, and a bracket. Among them, the rough sensing component consists of a siphon cup and copper foil to form a siphon triboelectric nanogenerator (Sp-TENG), with the copper foil evenly distributed on the outer wall of the siphon cup, and the material of this outer wall is fluorinated ethylene propylene (FEP); the precise sensing component consists of N single-tube triboelectric nanogenerators (St-TENG), and in this invention, 5 are taken as an example for illustration. The St-TENG mainly consists of water, an FEP tube, and copper foil. The water serves as one friction layer of the St-TENG, the FEP tube serves as the other friction layer of the St-TENG, and the copper foil serves as the electrode layer of the ST-TENG, and this St-TENG operates based on the single-electrode mode. On this basis, five St-TENGs are distributed in a way that the electrodes are evenly spaced and misaligned, and are installed on the siphon cup in a circular array manner, thus forming the precise sensing component. During the rainwater collection stage, when rainwater converges into the siphon cup of the rough sensing component through the rain receiving tray, the continuously rising rainwater levels in the siphon cup Sp-TENG and the multi-tube St-TENG will successively contact the copper foil, generating electrical signal information. When the rainfall intensity increases, the rising rate of the water level in the siphon cup increases, and the time interval for the water level to contact the copper foil decreases, so the electrical signal frequency of the TENG increases. In addition, due to the multi-tube collaborative sensing strategy of the precise sensing component, when the water level in the siphon cup rises, compared with the rough sensing component, the number of electrodes passed by the water level per unit time is more, indicating that the precise sensing component has a higher rainfall intensity detection accuracy; on the contrary, the rough sensing component, due to the large capacity of the siphon cup, has a larger range for detecting rainfall intensity compared with the precise sensing component. In summary, the rainfall intensity sensing unit can characterize the rainfall intensity through the TENG electrical signal frequency. In addition, when the water level in the siphon cup rises to the siphon start position, it can automatically trigger a siphon evacuation event, prompting the water level to quickly drop to the siphon stop position, thus completing a complete siphon working cycle, which is beneficial for continuously detecting rainfall information. At the same time, the siphon cup releases the accumulated rainwater potential energy through the siphon process, enabling the discrete and disordered raindrops in the environment to be converted into stable and ordered rainwater kinetic energy. Therefore, this device can also be used as a rainwater potential energy and kinetic energy conversion device with stable output energy.

[0007] The rainfall sensing unit includes a chassis support, a shaft, a water turbine, two rotary triboelectric nanogenerators (R-TENGs), and three flange couplings. The R-TENG consists of a rotor, a stator, copper foil, and polyimide (Kapton). The Kapton between the rotor and the stator serves as a friction layer, while the copper foil on the stator and the rotor serves as another friction layer and the electrode layer. The impeller of the water turbine is directly below the outlet of the rainfall intensity sensing unit, and the rotor of the R-TENG is coaxially connected to the water turbine. When the impeller of the water turbine is impacted by the water flow from the outlet of the siphon cup, it will generate a rotational motion, which will drive the R-TENG to work through the shaft, thereby generating an electrical signal. By establishing a positive correlation between the flow rate at the outlet of the siphon cup and the frequency of the electrical signal of the R-TENG, the frequency can be used to characterize the rainfall in the environment.

[0008] In addition, the rainfall sensing unit has a power generation function. When a siphon drainage event occurs in the siphon cup of the rainfall intensity sensing unit, the water flow at its outlet will drive the water turbine to rotate, thereby driving the TENG to work, and finally realizing the conversion of rain energy into electrical energy. Therefore, this device can be used as a power harvester with stable output energy. It can convert the disordered, fluctuating, and high-entropy rain potential energy in the environment into ordered, stable, and low-entropy electrical energy, which is beneficial to improving the energy conversion efficiency of this device.

[0009] Based on the self-powered sensing principle of characterizing rainfall intensity and rainfall amount by the frequency characteristics of TENG, the present invention has significant advantages in terms of measurement accuracy, range, and stability of rainfall sensing, and can provide a practical and reliable solution for wireless sensing detection of rainfall information. At the same time, this device can convert rain energy into electrical energy to supply power to other low-power sensors of wireless sensor network nodes, which is beneficial to expanding the networking range and node scale of wireless sensor networks. Generally speaking, compared with the prior art, the present invention has the following core advantages: 1. In terms of sensing, compared with the traditional sensing principle of characterizing rainfall intensity based on the voltage of TENG, the present invention has the core advantages of strong anti-humidity interference ability and good stability. At the same time, it can realize the self-powered sensing function of rainfall intensity without an external power supply; 2. In terms of power harvesting, compared with the traditional TENG raindrop power harvester, the present invention can convert the discrete, disordered, and low-energy raindrop energy in the environment into aggregated, ordered, and high-energy electrical energy, which can significantly improve the energy conversion efficiency of the device. Description of the Drawings

[0010] Figure 1 is a schematic diagram of the overall structure of a rainfall sensor based on a triboelectric nanogenerator according to the present invention;

[0011] Figure 2 is a schematic diagram of the structure of the rainfall intensity sensing unit of a rainfall sensor based on a triboelectric nanogenerator according to the present invention;

[0012] Figure 3It is a schematic structural diagram of a rainfall intensity sensing and precise measurement component of a rainfall sensor based on a triboelectric nanogenerator according to the present invention;

[0013] Figure 4 It is a schematic diagram of the electrode distribution of a rainfall intensity sensing and precise measurement component of a rainfall sensor based on a triboelectric nanogenerator according to the present invention;

[0014] Figure 5 It is a schematic structural diagram of a rainfall intensity sensing and rough measurement component of a rainfall sensor based on a triboelectric nanogenerator according to the present invention;

[0015] Figure 6 It is a schematic structural diagram of a siphon cup of a rainfall intensity sensing and rough measurement component of a rainfall sensor based on a triboelectric nanogenerator according to the present invention;

[0016] Figure 7 It is a schematic structural diagram of a rainfall amount sensing unit of a rainfall sensor based on a triboelectric nanogenerator according to the present invention;

[0017] Figure 8 It is a schematic structural diagram of a St-TENG of a rainfall amount sensing unit of a rainfall sensor based on a triboelectric nanogenerator according to the present invention;

[0018] Figure 9 It is a siphon principle diagram of a siphon cup of a rainfall intensity sensing and rough measurement component of a rainfall sensor based on a triboelectric nanogenerator according to the present invention;

[0019] Figure 10 It is a working principle diagram of a multi-tube St-TENG of a rainfall intensity sensing and precise measurement component of a rainfall sensor based on a triboelectric nanogenerator according to the present invention;

[0020] Figure 11 It is a working principle diagram of an R-TENG of a rainfall amount sensing unit of a rainfall sensor based on a triboelectric nanogenerator according to the present invention;

[0021] Figure 12 It is a method for detecting rainfall intensity and rainfall amount of a rainfall sensor based on a triboelectric nanogenerator according to the present invention;

[0022] In the figure: 1. Protection cylinder; 2. Water level sensing unit; 3. Rainfall sensing unit; 21. Sensing and precise measurement component; 22. Rough measurement component; 23. Support frame; 211. FEP tube; 212. Copper foil; 221. Siphon cup; 222. Copper foil; 2211. Water outlet; 2212. Exhaust port; 2213. Siphon stop position; 2214. Siphon start position; 31. Support base; 32. Shaft bracket 33. R-TENG 34. Flange 35. Water turbine; 36. Water isolation plate; 37. Shaft; 331. Rotor 332. Kapton 331. Stator. Detailed implementation mode

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] The following will further elaborate on the present invention in conjunction with the attached Figures 1-12 to further illustrate the present invention in detail.

[0025] An embodiment of the present invention discloses a rainfall sensor based on a triboelectric nanogenerator. Referring to the attached Figure 1 , a rainfall sensor based on a triboelectric nanogenerator includes a protection cylinder (1), a rainfall intensity sensing unit (2), and a rainfall amount sensing unit (3). The rainfall intensity sensing unit (2) and the rainfall amount sensing unit (3) are both arranged inside the protection cylinder (1), and the rainfall intensity sensing unit (2) is installed directly above the rainfall amount sensing unit (3).

[0026] Referring to the attached Figure 2 , the rainfall intensity sensing unit (2) is composed of a sensing precise measurement component (21), a sensing rough measurement component (22), and a support frame (23). Five St-TENGs of the sensing precise measurement component (21) are installed on the outer circumference of the siphon cup of the sensing rough measurement component (22) in a circumferential array manner.

[0027] Referring to the attached Figure 3 , the sensing precise measurement component (21) is composed of an FEP tube (211) and a copper foil (212), and the copper foil (212) is distributed on the surface of the FEP tube (211) as electrodes at equal intervals.

[0028] Referring to the attached Figure 4 , taking the distribution of the electrodes of the five St-TENGs in an equal-interval and misaligned manner as an example, the electrode distribution method of this component will be described. On the basis of the equal-interval distribution of the electrodes of each St-TENG, the electrodes of the five St-TENGs are misaligned in the vertical direction.

[0029] Referring to the attached Figure 5 , the sensing rough measurement component (22) is composed of a siphon cup (221) and a copper foil (222); the copper foil (222) is distributed on the outer wall of the siphon cup (221) at equal intervals. It should be noted that when installing the copper foil (222), it should be closely attached to the outer wall of the siphon cup (221).

[0030] Referring to the attached Figure 6, the siphon cup (221) of the sensing rough measurement component (22) is provided with a water outlet (2211) and a ventilation pipe (2212). The top position of the siphon can be used to set the siphon start position (2213) for starting the independent siphon drainage event of the siphon, and the end position of the ventilation port (2212) can be used to set the siphon stop position (2214) for closing the independent siphon drainage event of the siphon.

[0031] Refer to the appendix Figure 7 , the rainfall sensing unit (3) is composed of a support frame (31), a shaft bracket (32), an R-TENG (33), a flange plate (34), a water turbine (35), a water isolation plate (36), and a shaft (37); the impeller of the water turbine (35) is located directly below the outlet of the rainfall intensity sensing unit siphon cup (221), and the rotor (331) of the R-TENG is coaxially connected to the water turbine (35). Three flange plates (34) are respectively used to fixedly connect the water turbine (35), the R-TENG (33), and the shaft (37); two water isolation plates (36) are fixed to the support frame (31) with threaded fasteners and are respectively installed between the water turbine (35) and the two R-TENGs (33).

[0032] Refer to the appendix Figure 8 , the R-TENG is composed of a rotor (331), Kapton (332), and a stator (333). Copper foils are distributed on the side of the rotor (331) opposite to the stator (332), and the copper foils are distributed at equal intervals in a fan shape. Kapton (332) is a circular film, and when installed, one side is fixed to the copper foil of the stator (332), and the other side is in full contact with the copper foil of the rotor (331).

[0033] Refer to the appendix Figure 9 , explain the siphon principle of the device. When rainwater enters the siphon cup, the working state of the siphon cup enters the first stage of the siphon cycle from the initial stage, and the water level rises to reach the siphon stop height; the water level continues to rise until the working state of the siphon cup transitions from the second stage to the third stage, and the water level rises to reach the siphon start height. Thus, the siphon drainage event is triggered; due to the combined action of air pressure and water pressure, the rainwater in the siphon cup is quickly discharged from the outlet of the siphon cup under the continuous thrust, so the working state of the siphon cup enters the fourth stage, and the water level in the siphon cup quickly drops from the siphon start height to the siphon stop position, and the siphon ends, that is, the working state of the siphon cup returns to the first stage of the siphon cycle, and the rainwater is re-stored in the siphon cup.

[0034] Refer to the appendix Figure 10, taking the distribution of three St-TENG arrays of the sensing and precise measurement components in the rainfall intensity sensing unit as an example, the rainfall intensity sensing principle of this device is illustrated. Before the water level in the siphon cup reaches the first copper foil (copper electrode), since the FEP tube is more likely to acquire electrons than the copper electrode, they generate the same number of positive and negative charges respectively. When the water level reaches the first copper electrode of the first FEP tube, because the water covering the electrode carries positive charges, the original electrostatic balance between the FEP tube and the copper electrode is disrupted. At the same time, the induced potential difference drives electrons to flow from the ground to the copper electrode, thus generating a current signal in the external circuit. The current will continue until the water level completely covers the copper electrode. As the water level continues to rise, when the water level reaches the first copper electrode of the second FEP tube and the third FEP tube successively, corresponding current signals will also be generated. And so on, when the water level will successively contact the remaining copper electrodes in the three FEP tubes, corresponding electrical signals will be generated. According to the above principle, a positive correlation between the electrical signal frequency of the TENG and the water level rising rate can be established to achieve real-time detection of rainfall intensity. At the same time, it is easy to know that the detection accuracy of the rainfall sensing intensity of the device can be improved by increasing the number of FEP tubes or reducing the electrode spacing in each FEP tube.

[0035] Refer to the appendix Figure 11 , the working principle of the R-TENG in the rainfall amount sensing unit is described. After the siphon drainage event is triggered, the water flow at the outlet of the siphon cup of the rainfall intensity sensing unit will drive the rainfall amount sensing unit to work. The water in the container is discharged outward through the siphon drainage event, and stable fluid mechanical energy is formed through the outlet. At this time, the water flow impacts the water turbine (35) to drive the rotor (331) on the shaft (37) to rotate, causing the copper foil on the rotor (331) to rub against the Kapton (332) for charge transfer. The rotor drives the input electrode to move, and the overlapping position of the input electrode and the output electrode changes, breaking the electrostatic balance between phase a and phase b of the output electrode. The induced potential difference generated by the static charges drives the induced charges between phase a and phase b to be redistributed to balance the potential difference. In the load circuit connected to the output electrode, due to the flow of charges, a current flowing from phase b to phase a is generated. As the A phase of the input electrode coincides with the b phase of the output electrode, and the B phase of the input electrode coincides with the a phase of the output electrode, the device reaches electrostatic balance again. At this time, the a phase of the output electrode carries positive charges and the b phase carries negative charges, and there is no charge flow in the load circuit. As the rotor continues to move, the electrostatic balance is broken again, and the charges flow in the opposite direction in the circuit. At this time, a current flowing from phase a to phase b can be detected in the load circuit.

[0036] Refer to the appendix Figure 12, A method for detecting rainfall intensity and rainfall amount of a rainfall sensor based on a triboelectric nanogenerator. According to the above principle, when the rainfall intensity in the environment changes, the change in the rising rate of the rainwater level in the rainfall intensity sensing unit will ultimately be manifested in the change in the electrical signal frequency of the Sp-TENG and St-TENG. As shown in Figures (a) and (b), the coarse measurement component and the fine measurement component can respectively generate corresponding Sp-TENG and St-TENG electrical signal frequencies during the rising stage of the water level. Therefore, the real-time rainfall intensity can be reflected according to the real-time frequency characteristics of the TENG electrical signal, realizing the real-time detection of the rainfall intensity in the environment. In addition, as shown in Figure (c), when the siphon cup of the rainfall sensing unit triggers a siphon drainage event, the R-TENG will generate a decaying sine electrical signal. Therefore, the rainfall amount within a period can be reflected according to the frequency characteristics of the periodic decaying sine electrical signal of the R-TENG, that is, the detection of the average rainfall amount in the environment can be realized.

[0037] In summary, the present invention proposes a rainfall sensor based on a triboelectric nanogenerator, which can utilize the multi-tube collaborative sensing strategy, siphon drainage event and TENG self-driven sensing principle to cooperate with each other to realize the sensing detection of the real-time rainfall intensity and average rainfall amount change in the environment. At the same time, the raindrop energy can be converted into electrical energy to supply power for other low-power sensors.

Claims

1. A rainfall sensor based on a triboelectric nanogenerator (TENG), characterized in that: The sensor includes: a rainfall intensity sensing unit and a rainfall amount sensing unit. The rainfall intensity sensing unit consists of a rough sensing component and a fine sensing component, and can measure the rainfall intensity in real time through the TENG electrical signal frequency.

2. The rainfall sensor according to claim 1, wherein: The rainfall sensing unit includes a water turbine and a rotating friction nanogenerator (R-TENG), which drives the water turbine through the water flow of the siphon cup and simultaneously converts rainwater energy into electrical energy to power the wireless sensor network.

3. The rainfall sensor according to claim 1 has the advantages of rainfall sensing resistance to humidity interference, good stability and self-driving function, does not require an external power supply, and can efficiently convert random, low-energy-level rain energy into orderly, high-energy-level electrical energy.

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